This paper studies the co-movements of and the linkages between twelve Pacific-Basin stock markets during the June 1995-May 2005 period. We use the principal components analysis (PCA) technique to group the stock markets into statistically significant principal components in terms of the similarities of their index return movements. The rolling correlation analysis results show that correlation between the Pacific-Basin stock markets has considerable time-varying volatility. The Granger causality test results indicate that the weekly index returns of most Pacific-Basin stock markets are weak-form efficient and that most Pacific-Basin stock markets have significant lead/lag linkages. The study investigates the portfolio diversification implications of the linkages between the Pacific-Basin stock markets.